[PATCH v9 0/6] MCS Lock: MCS lock code cleanup and optimizations

[Tim Chen]

This update to the patch series now make mcs_spin_lock and mcs_spin_unlock
as inlined functions for better efficiency in the hot path.  We order the
files in the architecture of each Kbuild before we add mcs_spinlock.h for
hooking in architecture specific arch_mcs_spin_{lock,unlock}_contended
functions.

Peter, please review the last two patches and bless them with your
signed-off if they look right.

This patch series fixes barriers of MCS lock and perform some optimizations.
Proper passing of the mcs lock is now done with smp_load_acquire() in
mcs_spin_lock() and smp_store_release() in mcs_spin_unlock.  Note that
this is not sufficient to form a full memory barrier across cpus on
many architectures (except x86) for the mcs_unlock and mcs_lock pair.
For code that needs a full memory barrier with mcs_unlock and mcs_lock
pair, smp_mb__after_unlock_lock() should be used after mcs_lock.

Will also added hooks to allow for architecture specific
implementation and optimization of the of the contended paths of
lock and unlock of mcs_spin_lock and mcs_spin_unlock functions.

The original mcs lock code has potential leaks between critical sections, which
was not a problem when MCS was embedded within the mutex but needs
to be corrected when allowing the MCS lock to be used by itself for
other locking purposes.  The MCS lock code was previously embedded in
the mutex.c and is now sepearted.  This allows for easier reuse of MCS
lock in other places like rwsem and qrwlock.

Tim

v9:
1. Inline mcs_spin_lock and mcs_spin_unlock for better efficiency in hot paths.
2. Sort files in each architecutre's Kbuild before adding mcs_spinlock.h.

v8:
1. Move order of patches by putting barrier corrections first.
2. Use generic-asm headers for hooking in arch specific mcs_spin_lock_contended
and mcs_spin_lock_uncontended function.
3. Some minor cleanup and comments added.

v7:
1. Update architecture specific hooks with concise architecture
specific arch_mcs_spin_lock_contended and arch_mcs_spin_lock_uncontended
functions.

v6:
1. Fix a bug of improper xchg_acquire and extra space in barrier
fixing patch.
2. Added extra hooks to allow for architecture specific version
of mcs_spin_lock and mcs_spin_unlock to be used.

v5:
1. Rework barrier correction patch.  We now use smp_load_acquire()
in mcs_spin_lock() and smp_store_release() in
mcs_spin_unlock() to allow for architecture dependent barriers to be
automatically used.  This is clean and will provide the right
barriers for all architecture.

v4:
1. Move patch series to the latest tip after v3.12

v3:
1. modified memory barriers to support non x86 architectures that have
weak memory ordering.

v2:
1. change export mcs_spin_lock as a GPL export symbol
2. corrected mcs_spin_lock to references


Jason Low (1):
  MCS Lock: Optimizations and extra comments

Peter Zijlstra (2):
  MCS Lock: Order the header files in Kbuild of each architecture in
    alphabetical order
  MCS Lock: Allow architecture specific asm files to be used for
    contended case

Tim Chen (1):
  MCS Lock: Restructure the MCS lock defines and locking code into its
    own file

Waiman Long (1):
  MCS Lock: Barrier corrections

Will Deacon (1):
  MCS Lock: Allow architectures to hook in to contended paths

 arch/alpha/include/asm/Kbuild      |   5 +-
 arch/arc/include/asm/Kbuild        |   7 ++-
 arch/arm/include/asm/Kbuild        |   3 +-
 arch/arm64/include/asm/Kbuild      |   5 +-
 arch/avr32/include/asm/Kbuild      |  39 ++++++-------
 arch/blackfin/include/asm/Kbuild   |   5 +-
 arch/c6x/include/asm/Kbuild        |   3 +-
 arch/cris/include/asm/Kbuild       |   3 +-
 arch/frv/include/asm/Kbuild        |   3 +-
 arch/hexagon/include/asm/Kbuild    |   7 ++-
 arch/ia64/include/asm/Kbuild       |   5 +-
 arch/m32r/include/asm/Kbuild       |   3 +-
 arch/m68k/include/asm/Kbuild       |   5 +-
 arch/metag/include/asm/Kbuild      |   3 +-
 arch/microblaze/include/asm/Kbuild |   5 +-
 arch/mips/include/asm/Kbuild       |   3 +-
 arch/mn10300/include/asm/Kbuild    |   3 +-
 arch/openrisc/include/asm/Kbuild   |   9 +--
 arch/parisc/include/asm/Kbuild     |  27 +++++++--
 arch/powerpc/include/asm/Kbuild    |   6 +-
 arch/s390/include/asm/Kbuild       |   3 +-
 arch/score/include/asm/Kbuild      |   3 +-
 arch/sh/include/asm/Kbuild         |   7 ++-
 arch/sparc/include/asm/Kbuild      |   9 +--
 arch/tile/include/asm/Kbuild       |   3 +-
 arch/um/include/asm/Kbuild         |  30 ++++++++--
 arch/unicore32/include/asm/Kbuild  |   3 +-
 arch/x86/include/asm/Kbuild        |   1 +
 arch/xtensa/include/asm/Kbuild     |   3 +-
 include/asm-generic/mcs_spinlock.h |  13 +++++
 include/linux/mcs_spinlock.h       | 114 +++++++++++++++++++++++++++++++++++++
 include/linux/mutex.h              |   5 +-
 kernel/locking/mutex.c             |  60 +++----------------
 33 files changed, 275 insertions(+), 128 deletions(-)
 create mode 100644 include/asm-generic/mcs_spinlock.h
 create mode 100644 include/linux/mcs_spinlock.h

-- 
1.7.11.7


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